Cryoultramicrotomy, electron probe x-ray microanalysis and electron energy loss analysis will be used for high spatial resolution quantitation of the elemental composition of cells, organelles, membranes and extracellular space. The spatial resolution of electron probe analysis will be improved to 25 A and its detection sensitivity increased with a field emission gun, to develop it as a general approach for high resolution structural and compositional studies of muscle and muscle proteins. Electron energy loss analysis will be used for the enhancement of signal/noise with electron microspectroscopy, for the detection of low Z less than or equal to 12 elements and for obtaining information about chemical state at the ultrastructural level. Rapid freezing without cryoprotectants will be used for freeze fracture studies, and image processing techniques for the analysis of electron micrographs of cryo sections. Quantitative electron energy loss analysis and parallel detection techniques will be developed. The electron microspectroscopy techniques will be used for in situ studies on the subcellular distribution of ions, on biological phosphorylations and on the distribution of Ca, P and lipids in atherosclerotic blood vessels.